The present invention relates to a lapping machine, a lapping method and a magnetic head manufacturing method and, more particularly, a lapping machine and a lapping method capable of working a work with high precision, and a magnetic head manufacturing method using the lapping method.
In case the slider equipped with the magnetic head is formed, normally such slider is formed via the steps of forming a plurality of magnetic heads in a matrix fashion on a substantially disk-like substrate, then dividing the substrate into a plurality of pieces to form Bar-like (stripe-like) works, then shaping the works, and then dividing the works into chips every magnetic head. The chip-like substrate is employed as the slider.
In the steps of shaping the work, steps of forming a rail surface for the slider and lapping a part of the work are contained. The bar-like work is also called a xe2x80x9crow barxe2x80x9d on which at least the magnetic heads are aligned.
The lapping of the work is carried out to adjust a height of a magneto-resistive layer constituting the magnetic head and a height of the gap layer. Since the precision in the order of submicron unit is required for the height of the magneto-resistive layer or the gap layer, capable of working the work with high precision is needed.
In case the magnetic head is lapped, the lapping machine as set forth in Patent Application Publication (KOKAI) Hei 10-286765, for example, is employed.
As shown in FIG. 1, in case the work is lapped by the lapping machine, the work 101 is fitted to a lower surface of a lapping jig 102 in the situation that a top end of the magnetic head (not shown) on the work 101 is directed downward, and then the lapping jig 102 is fitted to an adaptor 103. Then, top ends of the work 101 and the magnetic head are lapped by a lapping surface plate 104. The work 101 is pushed against the lapping surface plate 104 by a pressure machine 105 via the adaptor 103 and the lapping jig 102. In addition, because the camber is generated in many works 101, all the magnetic heads on the work 101 are seldom brought into contact with an upper surface of the lapping surface plate 104 under the same conditions. For this reason, a lower end of the lapping jig 102 is pushed against the lapping surface plate 104 by one or three bending arms 106 that are passed through an opening 102a provided in the center of the lapping jig 102, and then a distribution of the pushing force to the lapping surface plate 104 on work 101 is adjusted by changing the pushing force, whereby the camber of the work 101 with respect to the upper surface of the lapping surface plate 104 is corrected.
Meanwhile, as shown in FIG. 1, in order to correct the camber of the work 101 by using one or three bending arms 106, top end positions of a plurality of magnetic heads being aligned on the work 101 must be successively changed along the work 101, as shown in FIG. 2. In other words, in the case of the state as shown in FIG. 2, the use of the bending arm 106 makes it easy to uniformize the lapping of a plurality of magnetic heads on the work 101. If the lapping of the top ends of the magnetic heads is carried out uniformly, characteristics of the lapping heads become constant.
However, in case the top ends of a plurality of magnetic heads aligned on the work 101 are arranged discontinuously as shown in FIGS. 3(a),3(b), it is difficult to correct the camber of the work 101 by using the bending arm 106. Thus, the characteristics of the magnetic heads on the work 101 after the lapping do not become uniform.
Such camber of the work 101 is generated by several causes. As the causes, for example, there are the alignment error generated when a plurality of magnetic heads are formed on one substrate by the thin film growing technology, or the alignment error of the mask employed to pattern the thin film on the substrate, or the minute undulation of the cutting surface generated when the works 101 are formed by cutting the circular substrate, or the chips generated by cutting the substrate, or the flatness difference of the work contact surface of the lapping jig 102, or the fine dusts that are present between the work 101 and the lapping jig 102, etc.
Also, as another problem, when the crown, the camber, or the twist, as shown in FIGS. 4(a) to 4(c), is generated in the shape after the work 101 is lapped, variation in a floating amount of the sliders obtained by dividing the work 101 or deterioration of the characteristics of the magnetic head is caused.
It is an object of the present invention to provide a lapping machine and a lapping method capable of lapping a work while correcting appropriately a camber of the work, and a method of manufacturing a magnetic head slider using the lapping method.
The above subject can be overcome by providing a lapping machine which comprises a lapping surface plate rotated by a rotating mechanism, a lapping jig having a plurality of projections to bottom surfaces of which a work to be lapped by a lapping surface on the lapping surface plate is fitted, variation-of-projection adjusting elements for adjusting the variation of the plurality of projections to the lapping surface plate individually, and a control circuit for outputting variation-of-projection control signals to the variation-of-projection adjusting elements.
In the lapping machine, preferably a plurality of resistive elements which are lapped by the lapping surface of the lapping surface plate are fitted to the work, and the control circuit has a function for calculating resistance values of the plurality of resistive elements.
Also, the above subject can be overcome by providing a lapping method which comprises the steps of fitting a bar-like work, which is lapped by a lapping surface of the lapping surface plate, to bottom surfaces of a plurality of projections of a lapping jig, adjusting a variation of the projections by variation-of-projection adjusting elements individually, and lapping the work by the lapping surface.
In the lapping method, preferably the work is separated between the projections before lapping of the work.
In the lapping method, preferably resistive elements arranged on the projections respectively are formed on the work, and resistance values of a plurality of resistive elements are measured, and then the variation-of-projection of the projections is increased as a resistance value is smaller.
According to the lapping machine and the lapping method of the present invention, a plurality of projections are provided to the lapping jig, the work is fitted to bottom surfaces of the projections, and a variation of the projections is adjusted individually. Therefore, discontinuous positional displacement of the work can be corrected at a plurality of locations individually by changing a variation of a plurality of projections individually, and thus the camber of the work can be corrected with good precision.
Also, in the case that the work is divided into a plurality of pieces finally, the operability can be improved if the projections are provided in the same number as the division and then the work is divided at spaces between a plurality of projections before or after the lapping of the work.
In addition, if the resistive elements are formed on the work, resistance values of the resistive elements are changed in compliance with the lapping of the resistive elements. Therefore, it is possible to grasp easily the lapping progress situation and the amount of camber by detecting the resistance values of all the resistive elements. Then, if a variation of the projections is changed based on the variation in magnitude of the resistance values of the resistive elements by the lapping, it is possible to render the amount of lapping of the work to coincide with the target value by making uniform the resistance values of the resistive elements.
Further, the above subject can be overcome by providing a magnetic head manufacturing method which comprises a step of forming a bar-like work on which a plurality of magnetic heads are aligned, a step of fitting the work to bottom surfaces of a plurality of projections of a lapping jig such that the magnetic heads are overlapped with the projections respectively, a step of adjusting a variation of the plurality of projections by a plurality of variation-of-projection adjusting elements individually, and a step of lapping the magnetic heads, whose top end positions are adjusted by adjusting the variation of the projections on the work, by a lapping surface of the lapping surface plate.
In the magnetic head forming method, preferably the work is divided into plural pieces between the projections before adjustment of the variation of the projections.
In the magnetic head forming method, preferably a plurality of resistive elements that are arranged on the plurality of projections individually are formed on the work, and resistance values of the plurality of resistive elements are measured respectively, and then the variation of the projections is increased as a resistance value is smaller.
According to the magnetic head manufacturing method of the present invention, a plurality of projections are provided to the lapping jig, the work on which a plurality of magnetic heads are aligned is fitted to bottom surfaces of the projections, and a variation of projection of the projections is adjusted individually. Therefore, discontinuous positional displacement of the work can be corrected at a plurality of locations individually by changing a variation of a plurality of projections individually, and thus the camber of the work can be corrected with good precision.
Also, in the case that the work is divided into chip-like sliders, the operability can be improved if the projections are provided in the same number as the division and then the work is divided between a plurality of projections before or after the lapping of the work.
In addition, if the resistive elements are formed on the work, resistance values of the resistive elements are changed in compliance with the lapping of the resistive elements. Therefore, it is possible to grasp easily the lapping progress situation and the amount of camber by detecting the resistance values of all the resistive elements. Then, if a variation of the projections is changed based on the variation in magnitude of the resistance values of the resistive elements by the lapping, it is possible to render the amount of lapping of the work to coincide with the target value by making uniform the resistance values of the resistive elements.
In this case, as the resistive elements, the monitoring dedicated resistive elements formed on the work may be employed, otherwise the magneto-resistive effect elements of the magnetic heads may be employed.
The above subject can be overcome by providing a magnetic head manufacturing method comprising the steps of fitting a bar-like work having a plurality of magnetic heads and a plurality of resistive elements, that are lapped by a lapping surface of a lapping surface plate, to a lower surface of a lapping jig, connecting a plurality of pushing/pulling mechanisms, that push down and pull up the lapping jig in a vertical direction with respect to the lapping surface, to a plurality of operation points of the lapping jig, measuring individual reference bending curves of the pushing/pulling mechanisms when a reference pushing/pulling force is applied to the lapping jig while selecting one of the pushing/pulling mechanisms sequentially, measuring a current shape of a lower surface of the work, setting a target shape of the work, calculating a correction shape that is a difference between the current shape and the target shape, calculating one pushing/pulling curve that is most approximate to the correction shape, by multiplying respective reference bending curves of the plurality of pushing/pulling mechanisms by an optimization ratio individually and then superposing them, and adjusting heights of the magnetic heads by lapping the work, the magnetic heads, and the resistive elements by virtue of friction between the lapping surface and them, while pushing/pulling the lapping jig to/from the lapping surface by the plurality of pushing/pulling mechanisms by applying pushing/pulling amounts, that are derived by multiplying the plurality of reference bending curves by the optimization ratio individually, to the plurality of pushing/pulling mechanisms.
According to the present invention, if pushing amounts or pulling amounts that are applied to a plurality of operation points of the lapping jig are optimized when the work that is equipped with the magnetic heads is lapped, the camber of the work and the curve obtained by connecting the top ends of the magnetic heads can be approximated to the target shape curve with high precision.
Moreover, the above subject can be overcome by providing a lapping machine which comprises a lapping surface plate rotated by a rotating mechanism, a lapping jig to a lower surface of which a work to be lapped by a lapping surface of the lapping surface plate is fitted, a sliding surface formed in the lapping jig, a plurality of pushing/pulling elements brought slidably into contact with the sliding surface, and a plurality of actuators for driving the plurality of pushing/pulling elements vertically with respect to the lapping surface.
According to the present invention, when the work is lapped, the pushing positions or the pulling positions applied to a plurality of operation points of the lapping jig can be optimized. Thus, the camber of the work can be approximated to the target shape curve with high precision.